1. Technical Field
The present invention relates to a spectroscopic measurement apparatus.
2. Related Art
There has been a known wavelength tunable interference filter that includes a pair of reflection films facing each other and picks up light of a predetermined wavelength from light under measurement by changing the distance between the reflection films (see JP-A-7-243963, for example).
The optical resonator (wavelength tunable interference filter) described in JP-A-7-243963 includes a first substrate having a recess formed in a surface thereof and a second substrate that blocks the recess, and the second substrate is so bonded to the first substrate that the interior of the recess is blocked. Further, high reflection films facing each other and electrodes that adjust the gap between the reflection films (inter-reflection-film gap) are provided on the bottom of the recess of the first substrate and the surface of the second substrate that faces the recess. The second substrate has a thick portion and a thin portion in an area facing the recess, and the thick portion can move toward and away from the recess when the thin portion is bent.
In the thus configured wavelength tunable interference filter, the inter-reflection-film gap can be adjusted by applying a voltage between the electrodes to deform the thin portion of the diaphragm and move the thick portion toward and away from the glass substrate.
To pick up light of a target wavelength through the wavelength tunable interference filter described above, a voltage according to the target wavelength is applied between the electrodes. At this point, since an electrostatic attractive force induced by the voltage application and an elastic force produced by the thin portion of the second substrate act on the thick portion of the second substrate, the thick portion oscillates.
In view of the fact described above, to measure light of the target wavelength in a precise manner, a spectroscopic measurement apparatus of related art using a wavelength tunable interference filter of this type waits until the thick portion stops oscillating and becomes stationary and then performs light level measurement after the thick portion stops oscillating and becomes stationary. The spectroscopic measurement apparatus of related art therefore has a problem of a long measurement period.